1. Field of the Invention
This invention relates to a noncontact type tonometer for discharging a fluid from a nozzle towards an eye to be tested to transfigure the eye and measuring the eye pressure thereof based on a fluid pressure when the eye has been transfigured by a predetermined amount.
2. Prior Art of the Invention
Heretofore, there has been known a noncontact type tonometer, in which a fluid such as an air pulse is discharged toward the cornea of an eye to be tested and the pressure of the eye is measured based on the pressure of the air pulse when the eye has been transfigured by a predetermined amount. However, this noncontact type tonometer has the shortcoming in that unless the vertical, rightward and leftward, and forward and backward alignments are accurate between the nozzle of a fluid discharging means for discharging an air pulse towards the eye and the vertex of the cornea of the eye, an error is occurred to an eye pressure value obtained by an eye pressure measuring means. In view of the foregoing, the conventional noncontact type tonometer is provided with an alignment detecting means for detecting the accurate alignment of the nozzle with respect to the eye to be tested.
If the nozzle of the fluid discharging means can be accurately aligned with respect to the eye using the alignment detecting means, an accurate eye pressure value can be obtained. However, since the eye to be tested is often accompanied with the problem of a minor fluctuation of the fixation of sight, the accurate alignment is difficult to obtain. Moreover, it takes much time to verify the alignment of the nozzle with respect to the eye to be tested. In addition, there is such a problem as that unless a person who has a long experience in such alignment verification, the accurateness of the alignment verification cannot be assured.